This study was conducted to investigate body‐mass‐index (BMI), insulin resistance and beta cell function in a group of pregnant women. Two hundred and twenty‐three consecutive women with an abnormal 50 g glucose challenge test in the third trimester were studied. All underwent oral glucose tolerance testing; 97 had a 100 g test and 126 a 75 g test. Fasting insulin was measured. Insulin resistance and beta cell function were calculated using the homeostasis model.

Among the 136 Caucasian, 60 Asian, 11 Indian and 16 Arabic women studied, there were no age differences. Arabic women had higher parity (p < 0.05). Asian women had lower BMI than Caucasian (p < 0.001), Indian (p < 0.01), and Arabic women (p < 0.01).

Women with gestational diabetes had higher insulin resistance than women with normal glucose tolerance (2.9 ± 4.0 vs 2.3 ± 2.5 p = 0.025). Women with gestational diabetes tended to have lower beta cell function 199 ± 203 vs 247 ± 380 p = 0.08). Asian women had higher glucose levels than Caucasian women after 50 g challenge (8.9 + 2.1 mmol/1 vs 8.6 ± 1.6; p = 0.034). Asian women were more likely to have gestational diabetes than Caucasian women (31.7% vs 14%; p = 0.02). Fasting glucose and insulin were comparable in Asian and Caucasian women. Mean insulin resistance and beta cell function in Asian and Caucasian women were not significantly different.

We concluded that Asian women had lower BMI than Caucasian women. Women with gestational diabetes were more insulin resistant. Insulin resistance and beta cell function in Asian and Caucasian women are similar. Gestational diabetes in Asian women is of similar aetiology to that seen in Caucasian women, but occurs at a lower BMI.